HP A005 manual Thermocompression Wedge Bonding, Material

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4.2 Thermocompression Wedge Bonding

In circuits where there is good access to the transistor chip bonding pads and to the circuit elements to which the chip bonds run, a variety of wedge bonders, including many new semi-automatic units, can be used. In situations where horizontal access is very limited (such as a transistor package), a manual machine with a small chisel wedge may be the most appropriate. The wedge does not have to be heated, but if it is the heater block temperature may be lowered slightly as specified in the next section. Since the exact amount of temperature adjustment required will vary from machine to machine, establishing the final temperature is an empirical process.

4.2.1 Wedge Bonding Procedure

4.2.1.1Set the heater block to 300°C ±10° for Si Bipolar transistors and 260°C ±10° for GaAs FETs.

4.2.1.2Wire diameters of 0.0005" to 0.001" are used most often, and the wire should be prestressed (annealed).

4.2.1.3Always make the bonds from the circuit element to the transistor bonding pads to minimize pad damage. Also, bonds should be made to the source and drain pads of an FET prior to making the bond to the gate pad. This minimizes the potential for electrostatic discharge damage (see section 6.0).

4.2.1.4Tip bonding pressure should be approximately 15 – 20 grams and should not exceed 20 grams. A good rule of thumb is that the “footprint” of the wedge on the gold wire should be about two wire diameters across (minimum of 1.5 and maximum of 2.5 diameters) for a good bond.

5.0 Material:
Vendor:	MWS
Wire:	0.0007 mil, P/N 453-18496, EL 1-3%
Vendor:	HYDROSTATICS INC.
Wire:	0.001 mil, P/N 453-010977-001, EL 3-8%
Vendor:	DEWEYL TOOL
Bonding
Wedge:	K-1/16-L-60-F1507-T1
Vendor:	GAISER
Bonding
Caps:	1/8", P/N 1251-15-35, (3-4-3)
	1/16", P/N 1551-15-375P-39 (3-5-5)
Vendor:	SEMI ALLOYS
Preforms:	0.6, P/N 10902-5
Vendor:	WILLIAMS PRECIOUS METALS
Preforms:	0.8, P/N 855-010982-006